MORPHOLOGY AND EVOLUTION
to the surfaces of the ilium by the sacro-iliac ligaments, of which there are three—an anterior ligament (A.S-I.L.j, a short posterior, and an oblique posterior (O.P.S-I.L.) ligament. The great sacro-sciatic ligament (Gr,S-S,L.) is a strong cord with expanded ends running from the sides of the lower sacral and coccygeal vertebrae to the ischial taberosity; it sends a process forwards to the sub-pubic ligament, and a band connects it to the rudimentary ischial spine, The small sacro-sciatic ligament (S.S-8.L.) runs from the lower end of the sacrum to the ischial spine. The symphysis pubis has the same ligaments as in Man. Keith (96) does not draw attention to any points in which the other Apes differ from the Chimpanzee in the characters of the pelvic ligaments ; he mentions the suggestion that the great sacro-sciatic ligament represents an ancient part of the tendon of origin of the biceps flexor cruris, but he regards it as part of the great lateral intermuscular septum. The curvatures of the vertebral column are described on page 136.
The Shoulder-joint — The ligamentous structures are more complex in the Chimpanzee than in the other Apes. In that animal there is a well-marked superior gleno-humeral ligament; it divides into two parts, which are attached separately to the hurnerus, and the sub-scapular bursa communicates with the shoulder-joint between them. Macalister (466) observed an inferior gleno-humeral ligament in the Gorilla. The posterior part of the capsule is weak and loose, but the anterior part has a broad anterior gleno-humeral ligament. Coraco-humeral and acromio-humeral ligaments are differentiated and the coraco-acrornial ligament is well